Two component polyurethane adhesive for wooden materials

Abstract

A two-component polyurethane adhesive for adhesively bonding wooden materials based on a polyol component A consisting of a) 10 to 98 wt. % of at least one oleochemical polyol, b) 1 to 7.5 wt. % of at least one diol having a hydroxyl value of 400 to 2000 and c) 1 to 7.5 wt. % of at least one tri-, tetra- or pentafunctional polyol having a hydroxyl value of 200 to 2000, the wt. % of each of a), b) and c) is based on the whole of the polyol mixture, and a polyisocyanate component B), wherein the NCO/OH ratio of components A) and B) is within the range of 1.5 to 0.9. The addition to the polyol component of 0 to 60 wt. %, based on the total weight of the polyol mixture, of a homogeneously dissolved resin, brings about a sharp increase in the adhesive strength. The adhesive maintains its strength even after boiling for 24 hours and drying for 7 days at 60° C. The adhesive is highly suitable for loadbearing structural members made of wood.

1 . A two-component polyurethane adhesive for wooden materials comprising components A and B wherein 
 A) is: 
 a polyol mixture, containing at least  
 a) 10 to 98 wt. % of at least one oleochemical polyol,  
 b) 1 to 7.5 wt. % of at least one diol having a hydroxyl value of 400 to 2000 and  
 c) 1 to 7.5 wt. % of at least one tri-, tetra- or pentafunctional polyol having a hydroxyl value of 200 to 2000, the wt. % of each of a), b) and c) based on the whole of the polyol mixture, and  
   B) is: 
 at least one polyisocyanate, wherein the NCO/OH ratio of components A) and B) is within the range of 1.5 to 0.9, and  
   further comprising from 0 to 85 wt. %, based on the total weight of the adhesive, of at least one auxiliary substance;    wherein the polyol mixture contains up to 60 wt. %, based on the total weight of the polyol mixture, of a resin homogeneously dissolved therein.    
     
     
         2 . The adhesive of  claim 1  wherein the resin is a natural resin.  
     
     
         3 . The adhesive of  claim 2  wherein the natural resin is a gum colophony or shellac resin, or derivatives thereof.  
     
     
         4 . The adhesive of  claim 1  wherein the resin is a synthetic resin.  
     
     
         5 . The adhesive of  claim 4  wherein the synthetic resin is a hydrocarbon, terpene, alkyd, furan, coumarone-indene, aldehyde or ketone resin, or a glycerol resin ester.  
     
     
         6 . The adhesive of  claim 1  wherein the oleochemical polyol comprises at least one polyol selected from the group consisting of castor oil, dimeric diols and polyols prepared by ring opening of epoxidised triglycerides of an olefinically unsaturated mixture of fats using alcohols.  
     
     
         7 . The adhesive of  claim 6  wherein the at least one polyol is castor oil.  
     
     
         8 . The adhesive of  claim 1  wherein the diol is at least one diol selected from among the alkanediols having 2 to 6 C atoms.  
     
     
         9 . The adhesive of  claim 8  wherein the alkanediols having 2 to 6 C atoms are selected from the group consisting of 1,4-butanediol, dipropylene glycol and diglycol.  
     
     
         10 . The adhesive of  claim 1  wherein the tri-, tetra- or pentafunctional polyol comprises at least one polyol selected from the group consisting of glycerol, pentaerythritol, propoxylated, ethoxylated ethylenediamine, and a tetraol.  
     
     
         11 . The adhesive of  claim 1  wherein the polyisocyanate is an aliphatic, cycloaliphatic or aromatic isocyanate having a functionality of 2 to 4.  
     
     
         12 . The adhesive of  claim 1  wherein the auxiliary substance is selected from the group consisting of fillers, catalysts, flow-control agents, and deaerating agents.  
     
     
         13 . A method of bonding wooden materials comprising applying to the wooden materials to be bound the adhesive of  claim 1 .  
     
     
         14 . The method of  claim 13  wherein the wooden materials are loadbearing wooden structural members.  
     
     
         15 . The method of  claim 13  wherein the water content of the wooden material during bonding is from 2 to 20 wt. %.